An advanced style of Stirling engine, now being considered for automotive applications, employs hydrogen under considerable pressure as the working fluid medium within a closed circuit for heat cycling. Reciprocating elements protrude into such closed circuit for extracting work energy from the heat cycling. Such elements also interconnect with a mechanical means for converting the reciprocal motion into rotary motion for propelling the vehicle. The latter mechanical means requires an oil flow to lubricate interengaging parts for appropriate long life functioning. Thus, the reciprocating elements must pass between two environments, one environment in which oil is freely distributed, preferably under a relatively high oil pressure, and the other environment in which hydrogen is employed as a heat transfer gas at extremely high pressures.
To maintain a separation between such environments and yet allow the reciprocating elements to pass therebetween, a sealing technique is employed which bleeds a small flow of hydrogen gas, from the working circuit, past the seal assembly separating the systems, to pick up oil scraped from the surface of the reciprocating elements by the seal elements. The mixture of gas and oil is then diverted to a remote location where oil is separated and trapped for return to the oil system and gas is reclaimed for return to the gas pressure systems.
A particular problem associated with separation concerns the mechanical means for performing the separation; it must operate under the stress of extremely high hydrogen gas pressure and must also function to promptly and periodically discharge the separated and collected oil back through an oil return line. A direct approach to this periodic discharge of oil is by use of a float valve assembly, the float being buoyant to actuate a valve in response to the attainment of a specific level of separated oil. Conventional float elements are detrimentally affected by the extremely high hydrogen gas pressure and cease to function after a short period of exposure to such environment.
Another problem associated with the separator apparatus is that, in certain applications, the seal assembly must withstand extremely high gas pressure on one side and withstand a relatively high oil pressure at the other side, and yet the seal elements must perform well over considerable cycles under very adverse temperature conditions.